GLACIATION OF PKINCE WILLIAM SOUND 469
great trunk glacier (PL CLXXXIV) to which the expanded Miles, Childs, Allen, Heney, and other glaciers were tributaries. This is indicated by the hanging valleys, as well as by oversteepened valley walls, eroded spurs, and the broadened valley bottom.
We realize that many problems are left unsolved, and, of these, one of the most interesting is the behavior of the Copper River during earlier stages of glaciation. At present, with its vast volume of water and its steep grade, it is able to compete with the glaciers and maintain mastery, though here and there diverted and transformed to rapids in the struggle, and in parts of its course burdened with a load of floating ice to be borne away. In earlier stages the struggle for mastery between river and glaciers must have been different, and some records of this struggle remain, but their exact interpretation calls for a much more detailed study than we were able to give.
These glaciers on the lower Copper Biver, and the glacial phenomena, are of more than ordinary interest, because of the fact that they lie along one of the highways to interior Alaska which promises to be of increasing importance in the immediate future. They will be easily accessible to the traveller from now on, and it is largely for this reason that we have devoted so much time to the glaciers and glaciation of the Copper River region, so that others may continue the work which we have merely commenced.
PRINCE WILLIAM SOUND
The Piedmont Glacier of Prince William Sound. It is clear that at the stage of maximum glaciation Prince William Sound was occupied by a great piedmont glacier. It was fed by the expanded valley glaciers of the fiords between Port Valdez and Orca Inlet on the east, by the enlarged ice tongues of Columbia Bay, Unakwik Inlet, Port Wells, and other fiords on the north, and by the Passage Canal, Port Nellie Juan and Icy Bay Glaciers on the west.
Its general extent is shown in PL CLXXXIV, a generalized map upon which no attempt has been made to show the complete seaward extent of this piedmont glacier.
It covered all of the lower islands and rose high upon the slopes of the tributary fiords, but, on some islands, high peaks rose through it as nunataks. Naked and Peak Islands, which are 1200 feet high, are shown by their rounded summits to have been completely overridden, as were Green and Perry Islands and the more irregular Lone Island. The nunataks were on Montague, Knight, and Hinchinbrook Islands where there are many horns and needles among the summit peaks.
The surface of the piedmont glacier may be restored in part, as is shown in the following table, in which some of the determinations of approximate heights of glaciation were made by Gilbert, some by Grant and Higgins, and some by the National Geographic Society's 1910 expedition. All altitudes are given in feet.
TABLE SHOWING HEIGHTS OF GLACIATION IN PRINCE WILLIAM SOUND
Harriman Fiord 4000 Latouche Island 2000
Columbia Bay 4000 Hinchinbrook Entrance 400
Port Valdez 8200 Orca Inlet 2300
The points in the first column are in northern Prince William Sound, those on the right hand are near the Pacific Ocean, and Hinchinbrook Entrance is about midway